The McGurk Effect is a fascinating auditory illusion where you can be fooled by what you are seeing into hearing something different. A remarkable property of the McGurk Effect is that even though you know you are being fooled, you still hear the wrong thing!

http://www.youtube.com/watch?v=G-lN8vWm3m0

What’s going on here is that when the brain tries to process a complex sound – and virtually all interesting sounds are indeed very complex – it tries first to create a model for what it thinks it is going to hear, and adapts what it actually hears to best match with the model. Since humans are primarily visually-driven beings, the brain will above all else try to match what we hear to what we see. This has some profound implications for listening to high-end audio, and understanding what it is you think you can hear.